(1) Field of the Invention
The present invention relates to generation of electrical power utilizing wind and, more particularly, to systems and methods for an increased efficiency wind power generator.
(2) Description of the Prior Art
At a time of both ever-increasing energy needs and non-renewable petroleum products to meet those needs, now is the time to consider the development and implementation of alternate energy sources. Wind generation of electricity is not a new idea; some believe the first wind generator was created by Poul la Cour in 1891 to generate hydrogen for the gaslights in his school. Since that time, a tremendous amount of engineering and development has gone into wind generators.
Bentz' law (formulated by the German Physicist Albert Bentz in 1919) states that you can only convert less than 16/27 (59%) of the kinetic energy of the wind to mechanical energy using a wind turbine. From research done in Denmark, a typical wind turbine generator runs at about 20% efficiency. This is primarily due to the effects of changing wind speed. For a particular wind turbine generator, calculations are made, based on the average wind speed for that area, to determine the optimum turbine and generator size. The maximum efficiency (typically about 40% to 50%) is reached at a particular wind speed. As the wind speed increases, the efficiency decreases.
Previous efforts to solve problems related to the above are described by the following patents:
U.S. Pat. No. 4,017,205, issued Apr. 12, 1977, to V. W. Bolie, discloses a vertical axis windmill having a horizontal base, preferably circular in configuration, sitting on the earth's surface, a dome having a horizontal bottom spaced above the base supported on a plurality of columns to provide an annular space below the dome bottom, a conical baffle positioned on the base below the dome, the conical axis being coincidental with the vertical axis of the dome, the dome having a circular roof orifice therein coaxial with the axis of the conical baffle, a vertical shaft supported coaxially by the conical baffle and an impeller affixed to the shaft and positioned in the dome circular orifice. Wind blowing relative to the windmill causes a lifting force by the aerodynamic effect of the dome, the wind passing upwardly through the annular opening and upwardly through the dome orifice, imparting rotational energy to the impeller. Power using apparatus such as generators or the like may be attached to the rotating vertical shaft. An alternate embodiment includes the utilization of a plurality of vertical vanes between the base and the dome, exterior of the conical baffle to more effectively direct the flow of air upwardly through the dome orifice.
U.S. Pat. No. 4,585,950, issued Apr. 29, 1986, to A. M. Lund, discloses multiple induction type generators drivingly connected to an impeller. As wind velocity increases, the generators are successively activated until all of the generators are operating at a maximum wind velocity. As the wind velocity decreases, the generators are successively de-activated until all of the generators are inoperative below a minimum wind velocity. Wind energy is more efficiently converted into electric power where impeller RPM must be maintained substantially constant under varying wind conditions to achieve the desired constant phase of the AC output.
U.S. Pat. No. 5,057,696, issued Oct. 15, 1991, to R. N. Thomas, discloses a vertical windmill employing aerodynamic lift includes stators that form an omnidirectional diffuser and can rotate out of the wind to reduce the destructive tendencies in high winds. A braking mechanism included in the windmill uses rotation of the airfoils to reduce the lift caused by the wind and disengagement of the airfoils to reduce nearly all lift on the airfoils. Centrifugal force is used to activate the brake in high winds, both to slow the rotor speed and, in extreme winds, to stop the rotor. A motor is provided to drive the windmill to simplify controls and increase energy production.
U.S. Pat. No. 5,518,362, issued May 21, 1996, to A. E. Kivilammi, discloses a method and wind power station for the utilization wind energy and transformation of wind energy into electrical energy. The wind power station comprises several rotors rotating by wind energy and connected to electricity producing generators. From these rotors the wind stream is directed also to a separate, main rotor to thereby maximize the output from a given stream.
U.S. Pat. No. 6,242,818, issued Jun. 5, 2001, to R. H. Smedley, discloses a vertical axis wind turbine having a plurality of blades around its periphery and a pivotable door associated with each blade. Each door has a pivot axis that is inclined outwardly toward the bottom of the turbine so that gravitational forces will pull the doors toward an open position. The doors are designed to move toward a closed position to at least partially block wind forces from the blades when the rotor rotates at potentially damaging speeds. The turbine has mating coils on the rotor and the support column to generate electrical energy when the rotor rotates.
U.S. Pat. No. 6,249,059, issued Jun. 19, 2001, to N. Hosoda, discloses a wind power device comprising a wind guide and a twisted member in the wind guide. The wind guide is rotatable around a vertical shaft so that a front opening of the wind guide may always face the wind. The wind which comes into the wind guide is guided around the twisted member and reaches to a blade wheel, which actuates a generator via gears to create electric power.
U.S. Pat. No. 6,448,669, issued Sep. 10, 2002, to D. M. Elder, discloses a turbine used to convert wind or fluid energy, and in some embodiments the kinetic energy of water, into mechanical energy, more specifically, a long axis type of vertical-axis turbine allowing large columns of air or water to be harnessed. These devices differ from horizontal-axis (propeller) type windmills or watermills which typically rotate about a vertical axis in order that they may face directly into a wind. The present invention is designed to be employed as a cost effective alternate power source in any wind or water current condition from a breeze to a gale wind, to a slow to moderate to fast water currents. To increase the structural integrity, the torque generating elements, namely, the rotor blades, are not directly attached to the shaft but rather, they attach to the round top and bottom rotor cage plates through which torque forces generated can be transferred to the shaft. The unique design of an open cover on the top of the wind or water turbine allows wind or water from the direction above the turbine to be harnessed. The top shield structure has created a calm wind or water area between the shield and the top of the rotor cage that helps reduce turbidity and greatly facilitates wind or water exhaust from the system.
U.S. Patent Application Publication No. 2002/0070558, published Jun. 13, 2002, to K. Johann, discloses a windmill for converting wind energy into electrical power and supplying it to a power grid, comprising a blade assembly, a generator housing, and a main shaft operatively coupled between the blade assembly and generator housing. The generator housing contains a first generator having a first generator output and a second generator having a second generator output. A hydraulic strut supports the generator housing and allows angular adjustment thereof. A hydraulic pump selectively pressurizes the hydraulic strut to effect adjustment thereof. A braking system is selectively actuable to slow rotation of the main shaft. A flyweight assembly and a four position speed sensing switch together detect rotational speed of the main shaft, selectively connect the generators with the main shaft, and selectively activate the braking system and hydraulic pump as appropriate according to the speed detected by the speed sensing switch.
The above patent applications do not describe a means for utilizing multiple generators and/or a variable wind dam for controlling windmill vertical rotor shaft rotational speed to thereby provide a substantially constant frequency output along with an increased efficiency wind power electrical generator. The solutions to the above-described problems have been long sought without success. Consequently, those skilled in the art will appreciate the present invention that addresses the above and other problems.